1. Technical Field
The present invention relates to printed circuit boards in general, and, in particular, to a printed circuit board having dielectric waveguide vias capable of transferring the AC component while blocking the DC component of electrical signals.
2. Description of Related Art
Different types of electronic devices can be mounted on one or both surfaces of a multi-layer printed circuit board (PCB). Transmission lines are typically utilized to route electrical signals among electronic devices. Transmission lines located on various layers of a PCB are interconnected with each other by means of a number of vertical connectors commonly known as vias.
Vias are typically filled with metal, but metallic vias are subject to many side effects that can degrade signal quality. For example, transitions to and from vias may cause an impedance discontinuity that can degrade signal quality. In addition, metallic vias may have stubs that can distort signal waveforms. The above-mentioned side effects become more pronounced when signal frequencies are increased.
In addition, metallic vias generate a DC connection between a trace in one layer of a PCB and a trace in another layer of the PCB. DC-blocking capacitors can be utilized to prevent DC connections; however, the addition of DC-blocking capacitors on the PCB may require more vias and extra board space in case of inner layer traces, which may lead to even more opportunities for signal discontinuity and loss. Capacitor parasitics from DC-blocking capacitors also cause signal degradation when signal frequencies are increased.
Consequently it would be desirable to provide an improved PCB that is free from the above-mentioned shortcomings.